Radio signaling means



D. G. LITTLE ET AL July 18, 1933, RADIO smmmne mums R 1 95 Original Filed Nov. 22 1926 WITNESSES; D d |NVENTOR5& dyw 0/2 0/ 6 diff/g A/arhan CD2 xba I). W BY ATT'ORNEY apparatus which can,

Reissued July 18, 1933 UNITED STATES PATENT OFFICE;

DONALD G. LITTLE; .oFnAsr SDBI GFIED JAND NATHAN GLDEFIBAUGIIJLYOF .LONG- MEADOW, MASSACHUSETTS, ASSIGNORS 'ro wnsriNen'ocs-nnnnormc A Dm Nm- .IEAG'TURING COMPANY, A CORPORATION or PENNSYLVANIA RADIO SIGNALING MEANS" Original N0. 1 ,707,271,'dated April 2,

reissue device used, for interrupting the continuous waves, usually called a chopper, includes a mechanical device driven by a'motor whichrequires more power than even a large vacuum tube. Moreover, the chopper is a noisy and frequently does, disturb the operators at the sending station.

The signal received froma station including a chopper is harsh andunpleasant to listen to. Such a signal cannot be as easily read as one which is a musicalznote. Experience shows that a signal, so faintjthat, it can hardly be heard, is more often perceived if musical than if harsh. g

It is an object of the present invention to produce a device frequency waves, which shalllproduce, an audio frequency above the keying frequency. The modulation preferably should be complete, causing no actual interruption but bringing the radio-frequency amplitude to zero,-for an instant only, once an audio cycle. The device can, if desired, be adjusted; to produce an interruption ateach cycle but, if this is done, the note begins to lose'its musical character. Y

It is a'further object of our-invention to a device for modulating the radiated I produce I waves which shall be quiet in operation and shall require only a small amount of power.

It is a further object of our invention to produce a devicefor modulating the radiated waves which shall givea musical'note in the receiving instruments.

It is a further ob]ect of our invention to produce a device for modulating the radiated waves which shall not cause severe strains in the tubes of the sending system.

It is a further object of our invention to provide a keying system by means of which a blocking potential the tubes when radiation is to be prevented.

It is a further object of our invention to provide such a keying system in which the blocking potential used shall not much exceed that necessary to prevent'the tubes from oscillating.

It is a further object of our invention to to generate continuous radiofor modulating the radio- I. 7

may be impressed upon I provide a keying system in which abrupt stopping and starting of the-oscillations in the several tubes are produced without excessive strain upon the tubes.

it is a further object f our invention to provide a blocking potential for the grids,

controlled by a key and supplied directly from the generator. whichenergizes the tubes.

Other objects of .our' invention will be apparent from the following detailed description and the accompanying drawing in which the single figure is a diagram of the circuits and apparatus. I

The vacuum tube l is connected to an adjustable inductor 2 and a condenser 3 which ar associated with it in any known way to constitute an oscillation generator. Energy for the generator is supplied from a highpotential direct-current source 4. An alternating-current source may, if preferred, be utilized but, if so, the tubes fed therefrom will be operative during only a part of thetime. A radio-frequency choke coilo protects the source l-from the oscillations'generated at the tube 1,;and a condenser of prevents a short circuit of the direct current of the source 4. If the source 4 be alternating, the condenser 6 must be=small enough to presenta large impedance to current therefrom. The-condenser 7 acts as the grid condenser for the tube 1 and is'connected, by the usual grid-leak resistor 8,; to the negative terminal,

the generator'i, andtheprimary 13-is associa-ted with a'secondary llb'y means of which the antenna 15 is energized.

The grids of the tubes 11 are provided with a grid-leak resistor 16 which is separated from the grids by a radio-frequency choke coil 17. The resistor 16 is connected to the negative terminal of the source 4 and thus to thefila'mentsof the tubes 11.

The connection between the resistor 16 and the negative terminal of the source 4 includes a parallel-resonant circuit comprislng an-inductor 21 and a condenser 22. The parallel resonant circuitis in the grid circuit of a tube 23 and constitutesa part of the feedback system by means of which the tube 23 is caused .to generate oscillations. The in ductor 21 is coupled with an inductor 24 in generated by the super-audio frequency. Such a generator would require arrangements, not shown herein, for rendering the signal perceptible.

Across the terminals'of the generator 4 a potentiometer resistor 25 is connected. The common connection of the filaments of the several tubesto the negative'terminal of the generator 4 is over a connection 26,'ad ustable along said potentiometer. A portion of the resistor 25 is thus included in series between the negative terminal of the-generator an dfthe filamentsa p 1 V key 27 is connected between the adjust.

able connection 26 and the negative terminal The several grid-leaks of the potentiometer; are also connected atfthe negative end of the potentiometer.

In the operation of the device, the oscillation generator 1 produces radio-frequency oscillations from I source '4. The radio-frequency oscillations are impressed over thecondenser 12 upon the gridsof the plurality of tubes '11. The tubes 11 are supplied with energy from thesource 4 which enables them to' act. as amplifiers controlled by frequency oscillations are thus" impressed,

over the transformer 1314, upon theantenna 15.

If the potential received by' the grids of the tubes 11 were controlled only by the master oscillator, the energy radiatedby the antenna would be unmodnlated. Unmodulated continuous radiation produces, in the tele= phones of the receiving sets, only a direct .currentand, consequently, can not be heard.

. Itj has beenusualto render the presence of the signal perceptible by interrupting the radiations, but .in our invention, the radiations are modulated rather than interrupted. This modulation is .producedby achange in potential of the grids of the tubes 11, obtained by superposing'an audio-frequency potential from the generator 23 upon the radio-frequencyfrom the master-oscillator'l and the steady potential resulting from the grid-leak; conne'ctionsthrough'the key 27. Y

Aslong'as the key 27 is closed, radiations are emitted by theantenna l5 and modulated :tials, therefore,

tor nor the amplifiers -the arc is extinguished energy supplied by the.

.whole potential of the the master oscillator. Radio- V pressedupon thegrid 1, serious strains would ing process.

actual embodiment,

current potential upon the grids of all of the tubes is that determined by the interact-ion of the several grid condensers 7, 12 and and .the'respective grid-leaks. The grid potenagevalue in each tube respectively.

When the key 27- is opened there 1s added, to the grid potentials ust mentioned, the drop over the portion of the resistor to the right of the contact 26. The contact 26 is so adj ust- .70 assume a characteristic averv ed thatthe additional negativepotential is sufiicientto cause each of the, tubes to be blocked. Oscillations of all of the tubes, therefore, cease.

It will be'observed that the tube 23 does 5 not use energy when it is: performing no useful function. It oscillates only when the radiations are being transmitted. It will also- 'be observed that neither the master oscillaare consuming energy When the key is open. 7

At;.the moment 'of opening the key 27 the negative potential impressed upon the grid of the tube 1 includes the drop over the are, which tends to form between the contacts of the-key. The grid,'therefore, becomes sufiiciently negative to render the tube 1 noncond'ucting, The path over which the arc is supplied thus becomes non-conductive, and so promptly thatit is not possible to perceive that any are ever forms. As soon as the are (which exists only theoretically) is extinguished, the negative potential impressed upon the grid of the tube 1 is only the drop over the right-hand part'of the r'esis tor25. This is suflicient to prevent the tube 1 from oscillating but is not even approximately as great as the whole negative potential of the generator' 4. If the generator 4 were im result, and the life of the tube would be materially shortened.

of the potentiometer for the whole of the yoltage ofthe generator lessens these strains lmpressedupon any of the tubesby'the key- In an embodiment of our device, actually built, a watt tube has been employed as the tube 23, where, by the methods of the prior "art, a chopper driven by a continuously running motor has been employed. In said ohms;. the resistor 16 was 3,000 ohms; the potential ofthe source 4 was 1,000 volts, the potentiometer resistor 25 was 40,000 ohms and andthepomt 26; was so adjusted that the potentialdrop across the right-hand part of the resistor 25 wassome 250 volts;

Although we have specifically described a the resistor 8 was5,000

viceis such as to prevent an arc, and, by the v substitution of the'potential over a portion single embodiment of our invention, it will be readily understood by those skilled in'the art that many variations may be made without departing from the spirit of this invention. \Ve, therefore, do not wish to be limited except as indicated in the claims or required by the prior art.

We claim as our invention:

1.' In a radio sending system, an antenna, means including a master oscillator and an amplifier for impressing a radio-frequency thereon, a grid-leak circuit including a resistor and a radio-frequency choke coil for said amplifier and means for impressing a periodic audio-frequency potential on said grid-leak circuit.

2. In a radio sending system, a master oscillator, an amplifier controlled thereby, an

audio-frequency oscillation generator oper atively associated with said amplifier to exert an additional control thereon and key-con-v trolled means for impressing a blocking potential sunultaneously on both generators.

3. Ina radio sending system, a master oscillator, an amplifier controlled thereby, an

audio-frequency oscillation generator operatively associated with said amplifier to exert an additional control thereon andkey-controlled means forimpressing a blocking p0- tential on said amplifier and simultaneously 011 both generators. a

4. In a radio transmitting system, a master oscillator comprising a triode, an amplifier comprising a tri ode, an audio-frequency generator comprising a triode, connections whereby said amplifier may be jointly controlled by said master oscillator and said audio-frequency generator; a common source of plate potential for said triodes,-and means whereby a blocking potential may be derived from said. common source and applied simulp ditional control thereon, and key-controlled taneously to the grids of said triodes.

5. In a radio transmitting system, a. master oscillator-comprising a triode, an amplifier comprising a triode, an audio frequency generator comprising a triode, connections whereby said amplifier may be jointly controlled by said master oscillator and said audio frequency generator, a common source of plate potential for said triodes, means for deriving a negative potential from said source, and a keying device for controlling the application of said negative potential to the grids of said triodes.

6. In a radio transmit-ting system, a master oscillator comprising a triode, an amplifier comprising a triode, an audio frequency generator comprising a triode, connections whereby said amplifier may be jointly controlled by said master oscillator and said audio-frequency generator, a common source of high potential for the plates of said triodes, a resistor connected in shunt to said source, connections from the grids of said triodes to the negative end of said source, connections mediate point on said resistor, whereby said grids are negatively biased with respect to said cathodes, and means for establishing a shunt around that port-ion of the, resistor which supplies said biasingpotential.

7. In a radio transmitting system, a master from the cathodes of said triodes to an interconnections whereby a grid-leak path associated with said amplifier is comprised in sa1d1nput-c1rcu1t, a common source of plate potent1al for said triodes, means for deriving a negative potential from said source, andad-,

ditional means for applying said negative potential at will to the grids of said triodes.

8. A system comprising an oscillator and an amplifier for amplifying waves from said oscillator, said oscillator and said amplifier each having a grid and a filament, means comprising two grid leak resistances connecting said oscillator and said amplifier, and a circuit comprising a switch connecting a point between said'resistances to said filaments.

9. In a radio sending system, a radio-frequency source, an amplifier controlled thereby, an audio-frequency source operatively associated with said amplifier to exert an additional control thereon, and means for impressing simultaneously on both said sources a potential adapted to substantially stop the fiow of all currents of said frequencies there- 1H.

10. In a radio sending system, a radio-frequency source, an amplifier controlled thereby, an audio-frequency source operatively associated with said amplifier to exert an admeans for impressing simultaneously on both said sources a potential adapted to substantially stop the flow: of all currents of said frequencies therein. I

' 11. In a radio sending system, a radio-frequency source, an amplifier controlled thereby, any audio-frequency source operatively associated with said amplifier to exert an additional control thereon and means for simultaneously blocking the flow of all signal-producing energy in both said sources and said amplifier.

12, In a radio sending system, a radio-free sources and said amplifier.

DONALD Gr. LITTLE. NATHAN vC. DEFIBAUGH. 

